Machine tool for the processing of rotating tools by means of a tool driven in synchronization with a work piece

ABSTRACT

Machine tool for machining of a rotating workpiece, comprising a tool drive, a workpiece drive for rotatably driving the workpiece, a tool rotationally driven by the tool drive in synchronization with the workpiece for producing a toothing on the workpiece, rotation transmitters for determining rotational condition of the tool and the workpiece, respectively, an electronic control for keeping the workpiece drive and the tool drive in synchronization by respectively associated ones of the rotation transmitters. A positioning motor is associated with one of the two drives for influencing the position of the phases of the two drives, and a sensor element provided in association with one of the two rotation transmitters is rotatably adjustable with respect to a stator of a corresponding one of the drives.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a machine tool for machining rotatingworkpieces by means of a tool, especially a fly cutter, rotatably drivenin synchronization with the workpiece, for producing teeth, withworkpiece drive and tool drive being kept in synchronism by respectivelyassociated rotation transmitters by means of electronic control means,with a positioning motor being associated with one of the two drives forinfluencing the position of the phases of the two drives.

In a known device of this kind (DE 41 14 341 C2), the stator housing atleast of the one motor is mounted concentrically with respect to themotor axis and is rotationally adjustable around this axis by means ofthe positioning motor. This means that the positioning motor is activelyengaged forcewise in the power flow of the drive and must therefore bedimensioned to be sufficiently strong.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a machine tool of this typein a manner such that it is simple to manufacture and that the shiftingof the phases can be achieved with low power requirement.

According to the invention a sensor element of one of the two rotationtransmitters is rotationally shiftable relative to the stator of thecorresponding drive motor.

As a result of such a formation, a machine tool according to theinvention is obtained in which a change in the position of the phases,directed forward or backward, of the two drives present in synchronousoperation is made possible with a reduced expenditure of force. Thestator housing need no longer be adjusted rotatably to produce thechange of the phases, but only the corresponding rotation transmitter.Therefore, the positioning motor can be designed to be small in terms offorce. In practice, this appears so that in order to change the phasesfor example for producing a helical toothing, the sensor element of therotation transmitter associated with the drive motor is adjustedrotatably depending on the pitch angle of the toothing. The synchronouscontrol associated with both drive motors thus causes are-synchronization while producing the phases-shifted synchronousoperation of the drives. It is possible for the rotation-adjustingsensor element to be associated with the drive motor for the toolspindle. Alternatively, however, the sensor element of the rotationtransmitter can be formed to be rotationally adjustable relative to thestator of the tool spindle drive motor. A modification of the conceptaccording to the invention that is favorable from a constructivestandpoint is characterized by the signal disc being arrangednon-rotatably on the drive shaft separated from the drive motor and bythe annular carrier being traversed freely rotatably by the shaft andbeing rotationally displaceable by the positioning motor. The annularcarrier is the carrier for the adjustable sensor element. For thepurpose of changing the condition of the phases in the synchronousoperation of the tool drive and workpiece drive, the positioning motoreffects a rotational displacement of the annular carrier. Initially, thesynchronous operation of the drive motors that are driven electricallyis re-regulated by means of the electronic control provided with suchmachine tools. Helical teeth can be produced by means of the formationaccording to the invention with an angle of maximum plus or minus 45°.In its turn, the annular carrier is likewise provided with a signal discthat is scanned by the sensor that is secured to the housing. By meansof this sensor, the angle of the phases can be detected by a CNC controlso that the corresponding command can be input from the latter for theproduction of a helical toothing for example. If there is no rotationaladjustment of the annular carrier together with the sensor elementmounted thereon, straight teeth will be produced on the workpiece. By acorresponding control with respect to the rotational adjustment of theconcerned sensor, nonlinear helical teeth could also be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

With the above and other objects and advantages in view, the presentinvention will become more clearly understood in connection with thedetailed description of a preferred embodiment, when considered with theaccompanying drawings of which:

FIG. 1 a schematic diagram of a machine tool in the vicinity of the twodrives for the tool spindle and workpiece spindle; and

FIG. 2 likewise illustrated simplified, shows partly in cross-sectionthe machine tool with the workpiece spindle aligned horizontally withtool spindle crossing the latter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Regarding the machine tool shown, it is a fly cutter milling machine.The latter has a workpiece spindle 2 that is mounted horizontally on themachine frame 1. The one end of the spindle carries a chuck 3 for a gearblank 4 to be provided with teeth.

A toothed pulley 5 is fixed non-rotatably on the workpiece spindle 2. Atoothed flat belt 6 guided around the pulley engages a drive pulley 7,which pulley is fixed on the drive shaft 8 of a drive 9 formed as anasynchronous motor. The stator 10 of the drive, which stator surroundsthe rotor, not shown, is fastened to the machine frame 1.

A tool spindle 11 extends crossing the workpiece spindle 2, the toolspindle in turn carrying a milling shaft 12 with a tool 13 that projectsradially and is formed as a fly cutter. The milling shaft 12 is causedto rotate by a drive 14 associated therewith, likewise formed as anasynchronous motor. Both drives 9 and 14 are kept in synchronizationwith one another by means of electronic control means. For this purpose,drive 14 has a schematically indicated first rotation transmitter 15.The latter registers the rotational speed of the drive 14 and transmitsthe rotational speed thus determined over a line 16 to a synchronizationcontrol device 17. A line connection 18 also runs from thissynchronization control device 17 to the drive 14.

A second rotation transmitter 19 is associated with the drive 9. Thisrotation transmitter however is not incorporated into the drive 9, butis provided in the vicinity of the workpiece spindle 2. In particular,this second rotation transmitter 19 incorporates a signal disc 20 withsensor element 21 associated with the signal disc, the signal disc beingnon-rotatably mounted on the drive shaft (workpiece spindle 2) separatedfrom the drive motor 9. The sensor element 21 is mounted on an annularcarrier 22 which carrier is freely traversed by the workpiece spindle 2.The annular carrier is freely rotatably mounted on a sleeve 23 thatsurrounds the workpiece spindle 2, the sleeve in its turn being flangedto the machine frame 1. The middle section 24 of the annular carrier 22is formed as a pulley. A toothed, flat belt 27 that runs to a pulley 25of a positioning motor 26 is positioned around this section 24. Thepositioning motor 26 in its turn is held in a fixed position on themachine frame 1 in a manner not shown.

On the side opposite to the sensor element 21, the annular carrier 22forms a signal disc 28 which in its turn cooperates with a sensor 29fastened on the flange 23' of the sleeve 23. The sensor 29 non-rotatablyarranged forms a third rotation transmitter 30 in conjunction with thecorresponding signal disc 28.

The production of a helical toothing 33 requires rotational displacementof the sensor element 21. This is accomplished by means of thepositioning motor 26, which rotates the annular carrier 22 relative tothe drive shaft and respectively workpiece spindle 2. The shift ofphases that thus occurs is registered by the rotation transmitter 19 asa deviation from synchronous operation and is transmitted over a line 31to the synchronization control device 17, which is connected throughanother line connection 32 with the drive 9. Now there resultsre-synchronization of either the drive motor 14 or the drive motor 9with attaining phases-shifted synchronous operation of workpiece drive 9and tool drive 14. The third rotation transmitter 30 is connected to theCNC control, not shown, of the machine tool. The corresponding angularposition of the sensor element 21 can be determined by comparing theoutput pulses of the rotation transmitters 19 and 30 which feed valuesto the CNC control.

We claim:
 1. Machine tool for machining of a rotating workpiece,comprisinga tool drive, a workpiece drive for rotatably driving theworkpiece, a tool rotationally driven by said tool drive insynchronization with the workpiece, for producing a toothing on theworkpiece, rotation transmitters for determining rotational condition ofsaid tool and said workpiece, respectively, electronic control means forkeeping said workpiece drive and said tool drive in synchronization byrespectively associated of said rotation transmitters, a positioningmotor associated with one of the two drives for influencing position ofphases of the two drives, and a sensor element provided in associationwith one of the two rotation transmitters, and means providing saidsensor element to be rotatably adjustable with respect to a stator of acorresponding one of the drives.
 2. Machine tool according to claim 1,whereinsaid one rotation transmitter further comprises a signal discnon-rotatably provided on a drive shaft separated from the correspondingdrive, and an annular carrier freely rotatably traversed by the driveshaft and rotatably displaceable by the positioning motor, said annularcarrier mounting thereon the adjustable sensor element.
 3. Machine toolaccording to claim 2, further comprisinga housing, a sensor mounted onthe housing, said annular carrier has a signal disc that is scanned bysaid sensor fixed with the housing.
 4. Machine tool according to claim2, wherein said drive shaft is a workpiece spindle carrying saidworkpiece.
 5. Machine tool according to claim 2, wherein saidcorresponding drive is said workpiece drive.
 6. Machine tool accordingto claim 1, wherein said tool is a fly cutter for producing teeth on theworkpiece.
 7. Machine tool according to claim 1, wherein said workpiecedrive is a drive motor.
 8. Machine tool according to claim 2, whereinsaid workpiece drive is a drive motor.
 9. Machine tool according toclaim 8, wherein said drive motor is an asynchronous motor.
 10. Machinetool according to claim 1, wherein said positioning motor is operativelyconnected to said sensor element for rotatably adjusting said sensorelement.
 11. Machine tool according to claim 1, wherein saidcorresponding drive is said tool drive.
 12. Machine tool according toclaim 1, wherein said workpiece drive and said tool drive areasynchronous motors.